Two Indian engineers continued to be in the custody of their abductors in Nigeria for the fourth day on Tuesday, even as the employers of the victims said they were 'trying their best to seek their early release'.

"We have received assurances from several quarters for the early release of the two men," Ajit Kakoty, father of kidnapped 32-year-old fire engineer Debashish Kakoty, told PTI from Sivasagar in Assam.

"Officials of the Indian High Commission in Lagos sent me an e-mail saying efforts were on for their release," he said. "The officials have also spoken to Lata, my daughter-in-law and said the delay in the release of the two men is because negotiations are not being held on a government-to-government basis."

Lata said officials of oil exploration Indorama are trying their best for the safe and early release of her husband and Sunil Dave of Maharashtra, who were abducted from their residential quarters in Nigeria's Port Harcourt on Saturday morning.

"They (company officials) have just said the two men will be released soon," Lata said.

The Indian government has said negotiations are being conducted by 'some private parties' and not the government as the kidnappers are purely criminal elements.

The abduction of the Indians is the latest in a string of kidnappings of foreign workers in Nigeria.